Life cycle of the camel tick Hyalomma dromedarii (Acari: Ixodidae) under field conditions in Northern Sudan

Text of Life cycle of the camel tick Hyalomma dromedarii (Acari: Ixodidae) under field conditions in...

Veterinary Parasitology 174 (2010) 305312

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Veterinary Parasitology

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Life cyc medunder

A. ELGhaa Central Veterb Department o n

a r t i c l e i n f o

Article history:Received 12 April 2010Received in reAccepted 23 A

Keywords:Camel tickHyalomma droLife cycleSudan

a b s t r a c t

Engorged Hyalomma dromedarii females were placed for development in shade and sun

1. Introdu

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(open non-shaded site) in April, August and December for two successive years. Engorgednymphs were also placed at the same sites in January, March, May, June, July and August.Preoviposition periods ranged between 9.8 and 11.7 days in the shade but longer in the sunin December (14.7 days). Egg production index was higher in August (0.72) than in Apriland December (0.46 and 0.39, respectively) in shade and in August compared to Decemberin the sun (0.65 and 0.29, respectively). In shade and in sun, the prehatching periods werelonger in December (50.7 and 48.2 days) than in April and August (25.6 and 29.0 days).Percentage hatchability ranged between 82 to 94.1% and 56.2 and 58.9% in the shade andsun, respectively. Number of eggs laid and eggs hatched were positively correlated withfemales engorgement weights. There were high mortality rates of females in the sun andmost of the eggs desiccated. Slight increased ambient and soil temperatures increased eggproduction, shortened preoviposition periods and decreased hatchability while increasedhumidity shortened preoviposition and prehatching periods and increased hatchability.

Nymphaladult moulting periods were long in January (20.7 days in the shade and 14.4days in the sun) and short in August in the shade (7.8 days) while they were only 6 days inMayand June in the sun.Highnumbersmoulted inallmonths in the shade (ranges23.329.5nymphs). The mean mortality of engorged nymphs in the shade was very low. However,in the sun mortality was high (12.930 nymphs). Premoulting periods were negativelycorrelatedwith ambient temperature but positively correlatedwith humidity. In the shade,mean number of nymphs moulting increased with increased mean ambient temperature,humidity and rainfall.

of total eggs produced by each female small batches of eggswere weighed and counted and accordingly the total eggswere estimated. By the end of hatching, larvae or the non-hatched eggs were counted and calculated as percentage

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highesDecemand oable 2halats winigheseenwar excethe mumberbatche, werDecemwas neen Au.001) hemalesds rangnicatwo-host when fed on rabbits. Ouheli (1994)that this tick is a three-host changing to two-heirdensityon thehostbecomeshigh.Alahmed2003) reported that this tick behaved as a two-en fed on rabbits. Recently, ELGhali andHassand that this tick behaved as a two-host tickn camels in Northern Sudan. This tick speciesed throughout the world wherever camels aresouthern Russia, in the Far, Middle and NearthAfrica and south of the great northern desertsmalilands and northeastern Kenya (Hoogstraal,presents nearly 90% of ticks infesting camelsl., 1963; Van straren and Jonjegan, 1993; Diab; ELGhali and Hassan, 2009). The economicof this tick species is considered as the camels

ant exporting animals in the Sudan and theirproduction are affected by high tick infestation.t work was conducted to study development H.under natural conditions aiming to identify thes of the tick development in Northern Sudan.of temperature, relative humidity, shade anddevelopmental periods are studied.

ls and methods

dy was conducted under eld conditions inn (Long. 3358E and Lat. 1740N) in RiverNorthern Sudan (at the junction of River Niletbara) where camels are reared and marketedmeanmaximumambient temperature is aboutmer (March to June) and the mean minimumperature in winter (October to February) falls10 C. The mean ambient relative humiditylow while the mean soil temperature rangesand 55 C in summer and ranges between 15winter.

as were divided into two sites shaded and open.nd maximum ambient temperatures, relativend soil temperature at ground level were daily09:00 and 15:00h and total daily rainfall wasd. In this aspect all thesemeteorological factorsred closely to the tested ticks.

ying and hatching

gorged H. dromedarii females were collectedls and immediately weighed and individually.5 cm2.5 cm glass vials, closed using cottonxed with adhesive tape. The vials were imme-ed in the eld at a depth of 35 cm and coveredroximately uniform thick layer of litter. A totalplicates were placed in the shade and a simi-in the sun at each area. This study was carriedmber 2001, April 2002, August 2002, December2003 and August 2003. Preoviposition, preeclo-s were daily recoded and number of eggs laidfor each female was estimated. For estimation